This whole Skolas escape and Xur coming to the tower has got me thinking more about the Nine. This is a possible theory that to me makes sense. What if the Nine are in a civil war. Not necessarily fighting but perhaps which side to join, a political war. Because Xur comes to the tower and helps us by trading with the Tower but at the same time they freed Skolas way after Xur started coming to the Tower. Currently the Nine are seen to be untrustworthy to the Reef but not to the Tower because Xur is still allowed to come.